1. Field of the Invention
The invention relates to a method for finding and digitally evaluating illegal image material.
2. Description of the Background Art
Searching through data memories for digital image material, evaluating the found image material digitally, and filtering it based on its content are known from the conventional art. In this regard, the image material to be evaluated can be single images and also image sequences in the form of films. This makes it possible, for example, for law enforcement agencies to analyze data memories of suspects in regard to illegal image material, for example, image material of sexual child abuse.
During the digital evaluation of the found image material, the image material is encoded by means of cryptographic hash functions and compared with cryptographic hash values of already known clearly illegal image material in relevant databases. If the cryptographic hash values match, then the image material found in the data memory is clearly illegal.
To find not yet captured illegal image material, the image material found in the data memory must be evaluated by visual inspection by individuals from law enforcement agencies. This relates to both completely new and also only slightly changed image material, already known per se, because the cryptographic hash values of the image material are changed even by a minor change in it and therefore no longer match the corresponding comparative image material or its cryptographic hash values in the databases. It is therefore not possible to digitally evaluate such new or changed image material to determine whether it is illegal image material.